UNITED STATESSECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549__________________________

FORM 8-KCURRENT REPORT

PURSUANT TO SECTION 13 OR 15(d) OF THESECURITIES EXCHANGE ACT OF 1934

Date of report (Date of earliest event reported): November 13, 2017 ( November 9, 2017)

TECOGEN INC.(Exact Name of Registrant as Specified in Charter)

Delaware(State or Other Jurisdiction of Incorporation)

333-178697 04-3536131(Commission File Number) (IRS Employer Identification No.)

45 First Avenue

Waltham, Massachusetts 02451(Address of Principal Executive Offices) (Zip Code)

(781) 622-1120(Registrant's telephone number, including area code)

_______________________________________________

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant underany of the following provisions:

o Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

o Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

o Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

o Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933(§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth companyþ

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complyingwith any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ¨

Item 2.02. Results of Operations and Financial Condition.

On November 9, 2017, the registrant issued via press release earnings commentary and supplemental information for thethree months ended September 30, 2017. The press release is furnished as Exhibit 99.01 to this current Report on Form 8-K.

The information contained in this Item 2.02 and Exhibit 99.01 to this Form 8-K shall not be deemed “filed” for purposesof Section 18 of the Securities Exchange Act of 1934 (the “Exchange Act”) or otherwise subject to the liabilities of that section,nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933 or the Exchange Act, except asexpressly set forth by specific reference in such a filing.

Item 7.01 Regulation FD Disclosure

On November 9, 2017, the Company presented the attached slides online in connection with an earnings conference call.Those slides are being furnished as Exhibit 99.02 to this Current Report on Form 8-K.

The information contained in this Item 7.01 and Exhibit 99.02 to this Form 8-K shall not be deemed "filed" for purposesof Section 18 of the Exchange Act or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated byreference in any filing under the Securities Act of 1933 or the Exchange Act, except as expressly set forth by specific reference insuch a filing.

Item 9.01 Financial Statements and Exhibits

(d) ExhibitsThe following exhibits relating to Item 2.02 and Item 7.01 shall be deemed to be furnished, and not filed:

Exhibit Description99.01 Press release dated November 9, 2017, for the three months ended June 30,

2017.99.02 Presentation dated November 9,

2017.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the Company has duly caused this report to besigned on its behalf by the undersigned, hereunto duly authorized.

TECOGEN INC. By: /s/ Bonnie BrownNovember 13, 2017 Bonnie Brown, Principal Financial & Accounting Officer

Tecogen Announces Third Quarter 2017 Results Tecogen has now Generated Positive GAAP Net Income in Four out of the Last Five Quarters WALTHAM, Mass., November 9, 2017 - Tecogen® Inc. (NASDAQ:TGEN), a leading manufacturer of clean energy products which, through patented technology, nearly eliminate criteria pollutants and significantly reduce a customer's carbon footprint, reported revenues of $8,501,198 for the quarter ended September 30, 2017 compared to $6,616,455 for the same period in 2016, or 28.5% growth in top line revenue. The completion of the merger with American DG Energy on May 18th added $1,556,115 in revenue to the quarterly result. Income from operations was $85,539 compared to $249,493 in the prior year comparable period. Similarly, Tecogen delivered net income for the quarter of $27,211 compared to $207,868 in the third quarter 2016. The quarter's results included non-recurring expenses totaling $37,445 related to the company's merger with American DG Energy. Depreciation and amortization jumped to $160,061 for the third quarter of 2017 from $66,484 for the same period in the prior year. The increase is related to the depreciation of the equipment that American DG Energy owns to deliver energy to its customers and the amortization of the corresponding contracts. Excluding merger related expenses, adjusted non-GAAP EBITDA(1) was a positive $295,755 for the third quarter of 2017 versus $382,802 for the third quarter of 2016, a decrease of $87,047. (Adjusted EBITDA is defined as net income attributable to Tecogen Inc, adjusted for interest, depreciation and

amortization, stock based compensation expense, and merger related expenses. See table following the statements of operations for a reconciliation from net income to Adjusted EBITDA as well as important disclosures about the company's use of Adjusted EBITDA). Commenting about the quarter, Tecogen Co-Chief Executive Officer Benjamin Locke noted, "Operationally, it was another positive quarter for Tecogen. The addition of revenue from American DG Energy more than offset lower product revenue, pushing total revenue to a quarterly record. With our backlog hovering near record levels, we are poised for a strong finish to the year. We have a handful of internal projects under way in the fourth quarter that should help to sustain our momentum going into 2018. We are rolling out an update of our Tecopower CHP unit, upgrading our chiller manufacturing capacity, and updating some internal software systems to improve our operational efficiency." Revenue results were driven by solid growth in services related revenues as well as the addition of energy production revenues provided by newly acquired American DG Energy. Total services related revenues for the third quarter of 2017 grew 20.0% over the prior year period, driven primarily by installation activity, while product revenue declined 14.9% compared to the third quarter of 2016. Chiller and heat pump sales more than doubled, partly offsetting a 30.2% decline from what were record cogeneration sales in the year-ago period. Changes in sales mix, partly offset by a full quarter of ADGE's high margin contribution, resulted in an 8.6% decline in gross margin to 38.3%

compared to 41.9% in the third quarter of 2016. Nevertheless, this remains well within management's targeted 35-40% gross margin range.

On a combined basis, operating expenses increased to $3,172,492 for the third quarter 2017 from $2,525,325 in the same quarter of 2016. An increase in selling expenses, which rose 37.0% to $503,415, merger related expenses of $37,445, and the consolidation of ADGE's core overhead, accounted for most of the increase. The increase in selling expenses was due to an uptick in marketing related activity and higher sales commissions. Backlog of products and installations was $14.5 million as of third quarter end, and stood at $16.8 million as of November 8, 2017. Speaking about the results Mr. Locke added, "The third quarter of 2016 was a breakout quarter for the company, but as such is a tough quarter to benchmark against. Despite that, the bottom line of this year's third quarter actually compares quite well. We had some remnant merger related expenses to take care of and we chose to increase the budget for selling expenses as an investment in future growth. Getting the merger with ADGE done required a lot of effort and non-quantifiable costs by management and administrative staff. Its successful completion was an important milestone for Tecogen and enables us to now focus squarely on that future growth. In all, I am quite pleased with how the quarter turned out." Co-CEO John Hatsopoulos said, “The third quarter showed the strategic importance of Tecogen’s acquisition of American DG Energy. It adds another stable stream of revenue to help cushion the ups and downs of our product revenue. We’ve now been profitable for five quarters in a row based on adjusted EBITDA(1) and are in a position of strength to meet the

opportunities that lie ahead."

Major Highlights: Financial • Gross profit for the third quarter of 2017 was $3,258,031 compared to $2,774,818 in the third quarter of 2016, an increase of 17.4% versus the same period in the prior year. This substantial growth was generated by the full-quarter contribution of American DG Energy. • Overall gross margin in the third quarter of 2017 decreased to 38.3% compared to 41.9% in 2016. A shift in sales mix to lower margin items was partly offset by the addition of high margin energy production revenue. • Product gross margin was 36.6% for third quarter of 2017 compared to 39.8% in third quarter of 2016 as revenue from chiller sales accounted for a larger portion of product sales compared to the year-earlier period. • Services gross margin declined to 34.0% in the period compared to the 43.5% in the prior year. Strong growth in lower margin turnkey installations accounted for the lion's share of the drop in margin. • Energy production gross margin was an exceptionally strong 53.5% following the completion of the merger with American DG Energy on May 18th. We would expect energy production gross margin to fluctuate materially due to seasonality. • On a combined basis, operating expenses rose to $3,172,492 for the third quarter of 2017 from $2,525,325 in the third quarter of 2016. The consolidation of ADGE's operations, $37,445 in merger related expenses and an increase in selling expenses to $503,415 from $367,412 accounted for most of the year-over-year increase. • Excluding non-recurring merger related costs and stock compensation expense, adjusted non-GAAP EBITDA(1) was $295,755 for the quarter compared to

adjusted non-GAAP EBITDA of $382,802 during the comparative third quarter of 2016. • Consolidated net income attributable to Tecogen, for the three months ended September 30, 2017 was $27,211 compared to $207,868 for the same period in 2016. • Net income per share was $0.00 compared to $0.01 for the three months ended September 30, 2017 and 2016, respectively. • Current assets at quarter end of $23,592,614 were more than double current liabilities of $9,399,283. Current liabilities include $850,000 of short-term debt due to a related party, which came to Tecogen via the acquisition of American DG Energy. Sales & Operations • Product revenues declined 14.9% from the same period in 2016. The launch of the InVerde e+ in early 2016 and uncertainty regarding the outlook for NYSERDA funding caused sales to jump in the second half of 2016. While cogeneration sales have pulled back 30.2% after last year's surge, they remain well above sales levels prior to InVerde's upgrade. In contrast, chiller sales increased 176.3% year over year. Increasing interest from both the indoor agriculture market and the growing recognition of the value proposition of "mechanical CHP" are the key drivers. • Services revenues grew 20.0% year-on-year, benefiting from increasing penetration in service contracts and favorable operating metrics for the installed fleet as well as an active period for installations work. Continued penetration of our 'turnkey lite' offering, which includes custom value-added engineering design

work as well as custom factory engineered accessories and load modules, has been a good source of services revenue growth and is expected to continue to develop as an important revenue stream. • Current sales backlog of equipment and installations as of Wednesday, November 8, 2017 was $16.8 million, driven by strong traction in the InVerde and Tecochill product lines and Installation services. As of September 30, 2017 the backlog was $14.5 million, in line with the Company’s goal of consistently delivering a quarter-end product backlog greater than $10 million. • Indoor agriculture continues to be a rapidly emerging new opportunity for growth, particularly for the Tecochill line of natural gas powered chillers. To-date, Tecogen has inked eight transactions in the space, all but one of which is to buyers who intend to grow cannabis. Interest for our products from new growers entering the market is ongoing. • On September 28th, Tecogen filed an 8-K declaring that it was exercising its right to terminate its TTcogen joint venture with Tedom. The 8-K also states that Tecogen "intends to work together with Tedom to come to an amicable decision to create a new path forward for TTcogen and the relationship between the Company and Tedom and/or facilitate an amicable wind up of TTcogen's affairs as provided for in the LLC Agreement and in accordance with the terms therewith." Emissions Technology • ULTRATEK - Subsequent to the quarter close, Tecogen announced that the Company and its co-investors have agreed to dissolve their Ultra Emissions Technologies S.à r.l. ("ULTRATEK") joint venture. The

dissolution process will take place under Luxembourg law and is expected to close by the end of the year. Once the process is complete, all unspent funds will be distributed to the ULTRATEK investors as agreed by a unanimous consent of the shareholders executed on October 24, 2017. As part of this disbursement, Tecogen will receive all its invested funds, $2 million in cash, and the sole exclusive IP that it licensed to ULTRATEK. Tecogen will then purchase all the non-cash assets of ULTRATEK, including all intellectual property, for $400,000. The IP includes two awarded patents, four patent applications, and all data and knowhow associated with the emissions testing performed by AVL. "The rigorous testing completed by ULTRATEK resulted in unassailable documentation and proof of the effectiveness of the Ultera process in reducing criteria emissions from gasoline-powered vehicles with no loss of performance or fuel economy," said Robert Panora, Tecogen President and COO. "Our engagement with both regulators and leading industry manufacturers has provided us with strategic insight regarding the path we should take to gain the confidence of the automotive industry that we possess a practical solution to a difficult problem, one that will neither be resolved in the near or medium term by electrification nor tolerated by the public and regulators. We very much look forward to taking this exciting technology to the next level."

• PERC - As reported in the last quarter of 2016, we received research grant funding from the Propane Education and Research Council (PERC) to demonstrate the viability of our emissions technology in fork trucks. The program’s goal is to develop a retrofit emissions system for fork trucks to reduce their emissions to levels more acceptable for air quality in indoor work environments. Earlier in the year, baseline testing of the unmodified fork truck was completed utilizing a donated fork truck from a major manufacturer that has expressed strong interest in Ultera and has agreed to assist our research effort. The data indicates that the fork truck is an excellent fit for Ultera technology, exhibiting an emissions profile that can be significantly impacted by our process. At this time, we have completed modification to the fork truck associated with the Ultera retrofit and are beginning shakedown testing of the system. Executives from the manufacturer and PERC are tentatively planning to visit Tecogen in December to view the prototype operation first hand. • California Air Permit for Ultera on Standby Generators - Now that facility technical staff have overcome some unrelated technical issues with the final generator, we are able to report that all generators at the facility have been retrofitted with the Ultera system and commissioned for their normal, intended use. Informal testing utilizing our portable emissions analyzers confirmed that all units are compliant to the Southern California standard. We anticipate the customer will complete third party “source testing” of the units, the final step in the permit process, in the upcoming month, at which

time we will have independent confirmation of our ground-breaking emissions reduction capability applied to this very stringent application. Conference Call Scheduled for Today at 11:00 am ET Tecogen will host a conference call today to discuss the third quarter results beginning at 11:00 am eastern time. To listen to the call dial (877) 407-7186 within the U.S. and Canada, or (201) 689-8052 from other international locations. Participants should ask to be joined to the Tecogen 3rd quarter 2017 earnings call. Please begin dialing at least 10 minutes before the scheduled starting time. The earnings press release will be available on the Company website at www.Tecogen.com in the "News and Events" section under "About Us." The earnings conference call will be webcast live. To view the associated slides, register for and listen to the webcast, go to http://investors.tecogen.com/webcast. Following the call, the webcast will be archived for 30 days. The earnings conference call will be recorded and available for playback one hour after the end of the call through Thursday November 23, 2017. To listen to the playback, dial (877) 660-6853 within the U.S. and Canada, or (201) 612-7415 from other international locations and use Conference Call ID#: 13672659. About Tecogen Tecogen Inc. designs, manufactures, sells, installs, and maintains high efficiency, ultra-clean, cogeneration products including natural gas engine-driven combined heat and power, air conditioning systems, and high-efficiency water heaters for residential, commercial, recreational and industrial use. The company is known for cost efficient, environmentally friendly and

reliable products for energy production that, through patented technology, nearly eliminate criteria pollutants and significantly reduce a customer’s carbon footprint. In business for over 20 years, Tecogen has shipped more than 2,300 units, supported by an established network of engineering, sales, and service personnel across the United States. For more information, please visit www.tecogen.com or contact us for a free Site Assessment. Tecogen, InVerde, Ilios, Tecochill, Ultera, and e+, are registered trademarks or trademark pending registration of Tecogen Inc. Forward Looking Statements

This press release and any accompanying documents, contains "forward-looking statements" within the meaning of the safe harbor provisions of the U.S. Private Securities Litigation Reform Act of 1995. Forward-looking statements can be identified by words such as: "anticipate," "intend," "plan," "goal," "seek," "believe," "project," "estimate," "expect," "strategy," "future," "likely," "may," "should," "will" and similar references to future periods. Examples of forward-looking statements include, among others, statements we make regarding: • The future structure and funding of Tecogen and any of its joint ventures. • The status of any intellectual property rights or assets. • Expected operating results, such as revenue growth and backlog. • Strategy for growth, product development, and market position. AND • Strategy for risk management. Forward-looking statements are neither historical facts nor assurances of future performance. Instead, they are based only on our current beliefs, expectations and assumptions regarding the future of our business, future plans and strategies, projections, anticipated events and trends, the economy and other future conditions. Because forward-looking statements relate to the future, they are subject to inherent uncertainties, risks and changes in circumstances that are difficult to predict and many of which are outside of our control. Our actual results and financial condition may differ materially from those indicated in the forward-looking statements. Therefore, you should not rely on any of these forward-looking statements. Important factors that could cause our actual results and

financial condition to differ materially from those indicated in the forward-looking statements include, among others, the following: • Competing technological developments. • Lack of market interest in our joint venture’s products. • Issues obtaining intellectual property protection. • Issues in the research and development of new products. • Tecogen’s inability to properly fund its joint ventures. AND • Such other factors as discussed throughout the "Risk Factors" section of Tecogen’s 10-K that was filed with the SEC on March 31, 2017 and can be found at www.sec.gov. Any forward-looking statement made by us in in this press release and any accompanying documents is based only on information currently available to us and speaks only as of the date on which it is made. We undertake no obligation to publicly update any forward-looking statement, whether written or oral, that may be made from time to time, whether as a result of new information, future developments or otherwise. Tecogen Media & Investor Relations Contact Information: John N. Hatsopoulos P: 781-622-1120 E: John.Hatsopoulos@tecogen.com Jeb Armstrong P: (781) 466-6413 E: Jeb.Armstrong@tecogen.com

TECOGEN INC. CONDENSED CONSOLIDATED BALANCE SHEETS As of September 30, 2017 and December 31, 2016 (unaudited) September 30, 2017 December 31, 2016 ASSETS Current assets: Cash and cash equivalents $ 2,077,047 $ 3,721,765 Accounts receivable, net 11,094,287 8,630,418 Unbilled revenue 3,063,089 2,269,645 Inventory, net 6,118,835 4,774,264 Due from related party 496,655 260,988 Prepaid and other current assets 742,701 401,876 Total current assets 23,592,614 20,058,956 Property, plant and equipment, net 15,502,974 517,143 Intangible assets, net 2,430,178 1,065,967 Excess of cost over fair value of net assets acquired 12,602,409 — Goodwill 40,870 40,870 Other assets 2,462,870 2,058,425 TOTAL ASSETS $ 56,631,915 $ 23,741,361 LIABILITIES AND STOCKHOLDERS’ EQUITY Current liabilities: Accounts payable $ 5,356,449 $ 3,367,481 Accrued expenses 1,676,307 1,378,258 Deferred revenue 1,477,124 876,765 Loan due to related party 850,000 — Interest payable, related party 39,403 — Total current liabilities 9,399,283 5,622,504 Long-term liabilities: Deferred revenue, net of current portion 386,494 459,275 Senior convertible promissory note, related party 3,149,086 3,148,509 Unfavorable contract liability 10,358,283 — Total liabilities 23,293,146 9,230,288 Commitments and contingencies (Note 9) Stockholders’ equity: Tecogen Inc. stockholders’ equity: Common stock, $0.001 par value; 100,000,000 shares authorized; 24,724,392 and 19,981,912 issued and outstanding at September 30, 2017 and December 31, 2016, respectively 24,724 19,982

Additional paid-in capital 56,081,026 37,334,773 Accumulated other comprehensive loss-investment securities (184,998 ) — Accumulated deficit (23,065,226 ) (22,843,682 ) Total Tecogen Inc. stockholders’ equity 32,855,526 14,511,073 Noncontrolling interest 483,243 — Total stockholders’ equity 33,338,769 14,511,073 TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY $ 56,631,915 $ 23,741,361

TECOGEN INC. CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (unaudited) Three Months Ended September 30, 2017 September 30, 2016 Revenues Products $ 2,425,616 $ 2,850,901 Services 4,519,467 3,765,554 Energy production 1,556,115 — Total revenues 8,501,198 6,616,455 Cost of sales Products 1,538,515 1,715,462 Services 2,981,454 2,126,175 Energy production 723,198 — Total cost of sales 5,243,167 3,841,637 Gross profit 3,258,031 2,774,818 Operating expenses General and administrative 2,427,352 2,003,838 Selling 503,415 367,412 Research and development 241,725 154,075 Total operating expenses 3,172,492 2,525,325 Income from operations 85,539 249,493 Other income (expense) Interest and other income 14,849 3,914 Interest expense (45,242 ) (45,539 ) Total other expense, net (30,393 ) (41,625 ) Consolidated net income 55,146 207,868 Income attributable to the noncontrolling interest (27,935 ) — Net income attributable to Tecogen Inc. 27,211 207,868 Other comprehensive income - unrealized gain on securities 39,361 — Comprehensive income $ 66,572 $ 207,868 Net income per share – basic $ 0.00 $ 0.01 Net income per share – diluted $ 0.00 $ 0.01 Weighted average shares outstanding – basic 24,720,613 19,640,812 Weighted average shares outstanding – diluted 24,930,624 20,229,120 Non-GAAP financial disclosure (1) Net income attributable to Tecogen Inc. $ 27,211 $ 207,868 Interest expense, net 30,393 41,625 Depreciation & amortization, net 160,061 66,484 EBITDA 217,665 315,977 Stock based compensation

40,645 66,825 Merger related expenses 37,445 — Adjusted EBITDA $ 295,755 $ 382,802

TECOGEN INC. CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (unaudited) Nine Months Ended September 30, 2017 September 30, 2016 Revenues Products $ 8,349,159 $ 7,525,909 Services 12,259,037 9,853,369 Energy production 2,330,307 — Total revenues 22,938,503 17,379,278 Cost of sales Products 5,261,245 5,035,230 Services 7,464,193 5,746,992 Energy production 1,053,741 — Total cost of sales 13,779,179 10,782,222 Gross profit 9,159,324 6,597,056 Operating expenses General and administrative 7,042,500 5,898,230 Selling 1,558,378 1,217,533 Research and development 641,064 524,696 Total operating expenses 9,241,942 7,640,459 Loss from operations (82,618 ) (1,043,403 ) Other income (expense) Interest and other income 21,033 9,575 Interest expense (115,026 ) (131,973 ) Total other expense, net (93,993 ) (122,398 ) Consolidated net loss (176,611 ) (1,165,801 ) (Income) loss attributable to the noncontrolling interest (44,933 ) 64,962 Net loss attributable to Tecogen Inc. $ (221,544 ) $ (1,100,839 ) Other comprehensive loss - unrealized loss on securities $ (184,998 ) $ — Comprehensive loss $ (406,542 ) $ (1,100,839 ) Net loss per share - basic and diluted $ (0.01 ) $ (0.06 ) Weighted average shares outstanding - basic and diluted 22,643,406 19,071,497 Non-GAAP financial disclosure (1) Net loss attributable to Tecogen Inc. $ (221,544 ) $ (1,100,839 ) Interest expense, net 93,993 122,398 Depreciation & amortization, net 402,939 198,766 EBITDA 275,388 (779,675 ) Stock based compensation

138,329 117,065 Merger related expenses 156,298 35,690 Adjusted EBITDA $ 570,015 $ (626,920 )

TECOGEN INC. CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS For the nine months ended September 30, 2017 and 2016 (unaudited) Nine Months Ended September 30, 2017 September 30, 2016 CASH FLOWS FROM OPERATING ACTIVITIES: Consolidated net loss $ (176,611 ) $ (1,165,801 ) Adjustments to reconcile net loss to net cash used in operating activities: Depreciation and amortization, net 402,939 198,766 Provision (recovery) of inventory reserve 43,609 (90,000 ) Stock-based compensation 138,329 117,065 Non-cash interest expense 577 37,923 Loss on sale of assets 2,909 640 Provision (recovery) for losses on accounts receivable 8,000 (6,000 ) Changes in operating assets and liabilities, net of effects of acquisitions (Increase) decrease in: Short term investments — 294,802 Accounts receivable (1,908,655 ) (2,664,462 ) Unbilled revenue (776,365 ) (1,024,276 ) Inventory, net (1,279,847 ) 714,896 Due from related party (236,971 ) 744,266 Prepaid expenses and other current assets (18,673 ) (100,398 ) Other non-current assets (32,251 ) — Increase (decrease) in: Accounts payable 1,641,206 (279,196 ) Accrued expenses and other current liabilities (233,824 ) 122,809 Deferred revenue 407,379 184,103 Interest payable, related party 21,378 — Net cash used in operating activities (1,996,871 ) (2,914,863 ) CASH FLOWS FROM INVESTING ACTIVITIES: Purchases of property and equipment (315,205 ) (130,499 ) Purchases of intangible assets (34,551 ) (71,223 ) Cash acquired in acquisition 971,454 — Cash paid for investment in Ultra

Emissions Technologies Ltd (2,000,000 ) Payment of stock issuance costs (367,101 ) — Distributions to noncontrolling interest (31,362 ) — Net cash provided by (used in) investing activities 223,235 (2,201,722 ) CASH FLOWS FROM FINANCING ACTIVITIES: Proceeds from demand notes payable, related party — 150,000 Payment of stock issuance costs — (28,548 ) Proceeds from debt issuance costs — (2,034 ) Proceeds from the exercise of stock options 128,918 312,698 Proceeds from exercise of warrants — 2,700,000 Net cash provided by financing activities 128,918 3,132,116 Net decrease in cash and cash equivalents (1,644,718 ) (1,984,469 ) Cash and cash equivalents, beginning of the period 3,721,765 5,486,526 Cash and cash equivalents, end of the period $ 2,077,047 $ 3,502,057

Supplemental disclosures of cash flows information: Cash paid for interest $ 95,550 $ 94,049 Exchange of stock for non-controlling interest in Ilios $ — $ 330,852 Issuance of stock to acquire American DG Energy $ 18,745,007 $ — Issuance of Tecogen stock options in exchange for American DG Energy options $ 114,896 $ — (1) Non-GAAP Financial Measures In addition to reporting net income, a U.S. generally accepted accounting principle (“GAAP”) measure, this news release contains information about EBITDA (net income (loss) attributable to Tecogen Inc adjusted for interest, depreciation and amortization, stock based compensation expense, and merger related expenses), which is a non- GAAP measure. The Company believes EBITDA allows investors to view its performance in a manner similar to the methods used by management and provides additional insight into its operating results. EBITDA is not calculated through the application of GAAP. Accordingly, it should not be considered as a substitute for the GAAP measure of net income and, therefore, should not be used in isolation of, but in conjunction with, the GAAP measure. The use of any non-GAAP measure may produce results that vary from the GAAP measure and may not be comparable to a similarly defined non-GAAP measure used by other companies.

NASDAQ: TGEN 3Q 2017 Earnings November 9, 2017

3Q 2017 Earnings Call 2 John Hatsopoulos •Co-Chief Executive Officer, Director Benjamin Locke •Co-Chief Executive Officer Robert Panora • President & Chief Operating Officer Bonnie Brown • Chief Accounting Officer Participants

3Q 2017 Earnings Call 3 This presentation This conference call and any accompanying documents, contain "forward-looking statements" within the meaning of the safe harbor provisions of the U.S. Private Securities Litigation Reform Act of 1995. Forward-looking statements can be identified by words such as: "anticipate," "intend," "plan," "goal," "seek," "believe," "project," "estimate," "expect," "strategy," "future," "likely," "may," "should," "will" and similar references to future periods. Examples of forward-looking statements include, among others, statements we make regarding: • Expected operating results, such as revenue growth, gross profit and backlog; and • Strategy for growth, product development, and market position. Forward-looking statements are neither historical facts nor assurances of future performance. Instead, they are based only on our current beliefs, expectations and assumptions regarding the future of our business, future plans and strategies, projections, anticipated events and trends, the economy and other future conditions. Because forward-looking statements relate to the future, they are subject to inherent uncertainties, risks and changes in circumstances that are difficult to predict and many of which are outside of our control. Our actual results and financial condition may differ materially from those indicated in the forward-looking statements. Therefore, you should not rely on any of these forward-looking statements. Important factors that could cause our actual results and financial condition to differ materially from those indicated in the forward-looking statements include, among others, the

following: • Decrease in interest in our products. • The elimination of incentives and rebates related to our products. • Competing technological developments. • Issues in the research, development, and commercialization of new products. • Tecogen’s inability to obtain sufficient funding. AND • Such other factors as discussed throughout the "Risk Factors" section of Tecogen’s 10-K that was filed with the SEC on March 31, 2017 and can be found at www.sec.gov. Any forward-looking statement made by us in this conference call and any accompanying documents is based only on information currently available to us and speaks only as of the date on which it is made. We undertake no obligation to publicly update any forward-looking statement, whether written or oral, that may be made from time to time, whether as a result of new information, future developments or otherwise. Safe Harbor Statement

3Q 2017 Earnings Call 4 Speaker Topic(s) John Hatsopoulos Introduction Benjamin Locke Why Tecogen 3rd Quarter Review Recent Achievements Robert Panora Emissions Update Bonnie Brown Financial Review Benjamin Locke Opportunities and Outlook Q&A 3Q Agenda

Heat, Power & Cooling that is Cheaper, Cleaner, & More Reliable Tecogen’s compelling ROI proposition meets the needs of a diverse range of customers. Hospitality Health Care Education Multi-Unit Residential Industrial Municipal Recreation “Unregulated Utility” CHP Modules Electricity & Heat Ilios Water Heaters 2-3x Heat Efficiency TECOCHILL Cooling & Heat Emissions Control Ultra-Clean Emissions Ultera On-Site Utility American DG ADGE 3Q 2017 Earnings Call 5 Why Tecogen?

REVENUE ▪ Total Revenues: $8.5M in 3Q17 vs. $6.6M in 3Q16 & $7.6M in 2Q17 ▪ Products: $2.4M in 3Q17 vs. $2.9M in 3Q16 & $3.1M in 2Q17 − Cogeneration sales declined after four quarters of robust year-over-year growth ▪ Service: $4.5M in 3Q17 vs. $3.8M in 3Q16 & $3.7M in 1Q17 − Growth primarily due to strong sales of full turnkey installations ▪ Energy Production: $1.6M in 3Q17 vs $774K in 2Q17 − 3Q17 was the first full quarter ADGE was consolidated within Tecogen PROFIT & Op. INCOME ▪ Gross Profit: $3.3M in 3Q17 vs. $2.8M in 3Q16 & $3.0M in 2Q17 ▪ Earnings from Operations: $86K in 3Q17 vs $249K in 3Q16 and a loss of $246K in 2Q17 − Selling and R&D expenses increased $224K combined year-over-year ▪ Adjusted EBITDA: $296K in 3Q17 vs $383K in 3Q16 and $64K in 2Q17 − Merger related expenses totaled $37K in the third quarter MARGIN ▪ Total Company gross margin of 38.3% in 3Q17 vs. 41.9% in 3Q16 ▪ Product and services gross margin eased to 34.9% vs 41.9% in 3Q’16 − Lower margin full turnkey installations were a greater share of revenue ▪ Energy production gross margin from ADGE of 53.5% in 3Q17 vs 57.3% in 2Q17 NET INCOME $27,211 in 3Q17 vs $207,868 in 2Q16 3Q 2017 Earnings Call 6 3Q’17 Results

Performance • Tecochill experiencing increasingly broad market penetration • Growing interest in full turnkey installation • Backlog sustained at near record levels Groundwork for Continued Growth • Expanding base of ESCO partnerships • Tracking state approvals for indoor grow facilities • Continued focus on improving ADGE fleet performance • Identifying and implementing cost savings measures of consolidated company Emissions Development for Future Growth • Completed prototype of fork truck emissions program • Completed installation of emissions packages on stationary generators seeking California air permit • Developing next steps to commercialize technology for automotive applications 3Q 2017 Earnings Call 7 Recent Achievements

Installed Base* Backlog $14.5M 3Q17 backlog vs $11.9M 3Q16 backlog $16.8M current Product and Installation Backlog as of November 8, 2017 Backlog growth driven by increasing demand for Chillers, InVerde e+, and Installation Services *Approximate recently installed base by end market as of YE 2016. 3Q 2017 Earnings Call 8 Multi-Unit Residential 41% Hospitality 5% Other 10% Industrial & Manufacturing 12% Education 20% Health Care 10% Recreation 4% Multi-Unit Residential 55%Hospitality 11% Other 16% Industrial & Manufacturing 8% Education 4% Health Care 5% Recreation 1% Backlog

3Q 2017 Earnings Call 9 As Delivered by Manufacturer With Ultera installed Tecogen Emissions Programs • PERC research grant for application of Ultera process to propane powered fork trucks – Retrofit complete on donated fork truck • As pictures to the right show, the technology fits well within existing machine architecture – Testing is now underway – Tecogen visits planned by partner and sponsor in the December timeframe • Ultera standby generator retrofit project in Southern California – All Ultera installations are complete following troubleshooting of unrelated technical issues – Third party “source testing” is anticipated to take place by year-end – NOTE: recent CPUC decision prohibits the use of fossil fuels for dispatchable demand response programs • No apparent restriction on non-dispatchable distributed generation capacity for peak shaving Emissions Update

Ultera Adaption to Vehicle Emissions • Dissolution of Ultratek pending – Tecogen to receive $2 million in cash – Transaction to acquire all the IP within Ultratek for $400,000 to follow • Initial conversations with investors in new entity underway • Goal is to have structure in place to begin research & development process in early 2018 3Q 2017 Earnings Call 10 Emissions Update

Financial Metrics Revenues, Margins, Growth ▪ Four revenue streams − Product sales − Long-term service contracts provide stable ongoing revenue − Turnkey Installation through Tecogen service operations − Energy production through wholly-owned subsidiary, ADGE, provides additional source of stable ongoing revenue ▪ Maintain Gross Margins at 35% - 40% ▪ Quarterly Product Backlog >$10M ▪ Future energy revenues (undiscounted) > $50M Tecogen Revenue Model & Outlook ✓ Record quarter-end backlog of $14.5 million 3Q 2017 Earnings Call 11 2017 Quarter Ended September 30 Y/Y % of Total 2017 2016 Growth Revenue REVENUE Cogeneration 1,842,185$ 2,639,713 21.7% Chiller (includes HEWH) 583,431 211,188 6.9% Total Product Revenue 2,425,616 2,850,901 -14.9% 28.5% Service Contracts & Parts 2,109,654 2,113,295 24.8% Installation Services 2,409,813 1,652,259 28.3% Total Service Revenue 4,519,467 3,765,554 20.0% 53.2% Energy Production 1,556,115 - 18.3% Total Revenue 8,501,198$ 6,616,455$ 28.5% 100.0% COST OF SALES Products 1,538,515 1,715,462 Services 2,981,454 2,126,175 Energy Production 723,198 - Total Cost of Sales 5,243,167$ 3,841,637$ 36.5% Gross Profit 3,258,031$ 2,774,818$ 17.4% 38.3% Net income attributable to Tecogen Inc 27,211$ 207,868$ GROSS MARGIN Products 36.6% 39.8% Services 34.0% 43.5% Products & Services GM 34.9% 41.9% Energy Production 53.5% N/A Overall Gross Margin 38.3% 41.9%

3Q 2017 Earnings Call 12 Sustained Positive Results Five Consecutive Quarters of Positive Operational Results ▪ Adjusted EBITDA of $730K over the last four quarters ▪ Sustained step change in profitability that was first achieved in 3Q’16 ▪ Reinvesting profits back into the business − $457K increase in selling and R&D expenses over the first nine months of 2017 versus 2016 − Increased focus on product development and customer outreach Non-GAAP f inancial disclosure Q3 2017 Q3 2016 Net Income (loss) attributable to Tecogen Inc. 27,211$ 207,868$ Interest expense, net 30,393 41,625 Depreciation & amortization, net 160,061 66,484 EBITDA 217,665 315,977 Stock based comp nsation 40,645 66,825 Merger related expense 37,445 - Adjusted EBITDA 295,755$ 382,802$ -$1,500 -$1,000 -$500 $0 $500 20 14 Q1 20 14 Q3 20 15 Q1 20 15 Q3 20 16 Q1 20 16 Q3 20 17 Q1 20 17 Q3 Adjusted EBITDA Quarterly with T4Q Average (dotted line) - $Thousands Sustained step change to profitability

$0 $2 $4 $6 $8 $10 $12 $14 $16 $18 20 14 Q 1 20 14 Q 3 20 15 Q 1 20 15 Q 3 20 16 Q 1 20 16 Q 3 20 17 Q 1 20 17 Q 3 Revenues Trailing 4 Quarters - $ Millions Products Services Energy Production (ADGE) 3Q 2017 Earnings Call 13 Consistent Financial Progress 30% 32% 34% 36% 38% 40% 42% 20 14 Q 1 20 14 Q 3 20 15 Q 1 20 15 Q 3 20 16 Q 1 20 16 Q 3 20 17 Q 1 20 17 Q 3 Gross Margin Trailing 4 Quarters (%) $0 $2 $4 $6 $8 $10 $12 $14 $16 $18 De c-1 4 Ma r-1 5 Jun -15 Se p-1 5 De c-1 5 Ma r-1 6 Jun -16 Se p-1 6 De c-1 6 Ma r-1 7 Jun -17 Se p-1 7 Backlog - Product and Installation Services: $Millions $0 $2 $4 $6 $8 $10 $12 $14 20 14 Q 1 20 14 Q 3 20 15 Q 1 20 15 Q 3 20 16 Q 1 20 16 Q 3 20 17 Q 1 20 17 Q 3 Op ating Expense Trailing 4 Quarters - $Millions

Opportunities & Outlook a growing company in a growing industry •High ROI product •Technological innovation •Relationships with key partners •Increasing environmental and regulatory pressures •Resiliency and Demand Response concerns Sales •Turnkey installation •Long term service agreements •Nationwide presence •High margin revenue stream •Additional growth anticipated Service •Predictable, annuity type revenue •Enhancing profitability of existing fleet •Reduced operational costs through Tecogen service •Additional growth possibility American DG •Double digit CAGR •>$40B market potential for CHP •Margins 35% - 40% •>$10M product and installation backlog •<50% manufacturing capacity utilization •Stable operating expense profile Growth & Margins 3Q 2017 Earnings Call 14

NASDAQ: TGEN 3Q 2017 Earnings Call 15 Q & A

Company Information Tecogen Inc. 45 First Avenue Waltham, MA 02451 www.tecogen.com Contact John Hatsopoulos, Co-CEO 781.622.1122 John.Hatsopoulos@tecogen.com Jeb Armstrong, Director of Capital Markets 781.466.6413 Jeb.Armstrong@tecogen.com 3Q 2017 Earnings Call 16 Contact Information